The invention herein is directed primarily toward new and useful improvements in apparatus for the trimming and selective pruning of hedges, shrubs, trees, and the like.
Conventionally, the basic trimming operations heretofore have been effected by use of standard electric or gas hedge trimmers. Such trimmers, in their best known form, consist of two overlying blades, either both reciprocally driven or one fixed and one driven. Each of the blades incorporates at least one working edge with projecting shearing knives into which the plant growth is selectively introduced for a subsequent severing thereof during the reciprocating action. Such trimmers, while extremely efficient on smaller branches, tend to be less than satisfactory as the size of the individual branches increase. The larger branches or limbs must in effect be gnawed off by the shearing action of the trimmer knives rather than being severed by a single shearing stroke. This in turn produces a ragged and unsightly cut which becomes worse as the diameter of the limb increases because of the longer time to actually effect the cut.
The problem of accommodating heavier branches encountered during trimming operations has become increasingly difficult in light of recently introduced safety standards. For example, the Consumer Product Safety Commission has caused standards to be drawn up relative to the spacing of the trimmer knives to satisfy minimum safety trimmer requirements. Pursuant thereto, Underwriters Laboratories Inc., in its standard for electric hedge trimmers, revised paragraph 22.1 effective Mar. 24, 1978, notes that the blade assembly of a hedge trimmer shall be such that 0.75 inch (19.1 mm) diameter cylindrical probe applied to the blade assemblies with its axis normal to the shearing plane does not contact the shearing area. Industry has, in some instances, been even more stringent, requiring a spacing which will accept only a maximum diameter of 0.437 inch. With such standards, it will be appreciated that much of the peripheral larger branch or limb severing normally attempted with a conventional hedge trimmer will now be impossible.
While the trimming or pruning of larger trees and the like can be effected by power chain saws, such saws have been found to be potentially quite dangerous, particularly when attempting the use thereof on branches on the order of approximately three inches in diameter or less. This is due, in large part, to the flexibility or lack of beam strength in the branch, as well as the manner in which the cutting itself is effected. Further, the resultant cut while acceptable for rough lumber, would be unacceptable for ornamental shrubs, trees and the like.
The patent to C. E. Jenkins, U.S. Pat. No. 2,573,573, issued Oct. 30, 1951, discloses another form of power-driven wood saw wherein a reciprocating cutting action is involved using either a single blade or a pair of blades riveted together. This saw is intended for the cutting of logs, felling of tress, and other rough cutting operations. There appears to be no suggestion of the use of such a saw, or in fact an indication of the adaptability of such a saw, for the cutting of smaller branches such as might be encountered in the trimming or pruning of hedges, shrubs or the like in a home environment.
Page 99 of the September, 1979 issue of Popular Science refers to a saber saw on a hedge trimmer with a lever-operated clamp to cut heavy growth up to one inch diameter.